To provide an image pickup device that causes no deterioration in image quality even when an incident luminous quantity is less.

In the case that the incident luminous quantity detected by a luminous quantity detection circuit 110 is a prescribed value or below and a numerical aperture of a mechanical diaphragm unit 103 is maximum (open) and an applied voltage to a physical property restriction unit 104 is a voltage corresponding to the highest transmissivity, a luminous quantity control circuit 112 controls a physical property drive means 118 to move the physical property restriction unit 104 from a position on an optical path to the outside of the optical path.